1. Field of the Invention
The present invention relates to torches. More particularly, it relates to cutting torches, either the straight type or the attachment type, having manually operated valve mechanisms to control cutting oxygen flow rate. In a particular aspect, the invention is concerned with an improvement in cutting torches employing diaphragm type (packless) cutting oxygen valve mechanisms.
2. Background of the Related Art
Cutting torches supplying gaseous oxygen/fuel gas mixtures through cutting nozzles to produce pre-heating flame temperatures sufficiently elevated to reach the melting point of, for example, carbon steel, and also supplying commercially pure oxygen through a separate passageway to effect a cut by burning through the material, have been produced in many forms.
Conventional manually operated cutting torches have incorporated cutting oxygen valve mechanisms employing packed valve stems to seal internal regions which are pressurized with gaseous oxygen from the exterior (atmosphere). Some such packed cutting oxygen valve designs have, additionally, incorporated some type of gas flow rate metering device to enable the operator of the torch to control the flow rate of gaseous oxygen through the cutting oxygen valve and nozzle by selective positioning of the valve operating mechanism. Such cutting oxygen flow rate control is desirable in order to facilitate performance of the cutting process while improving the quality and the precision of the resulting cut.
Cutting torches of the packed stem cutting oxygen valve type present certain difficulties and inconveniences which are inherent in the packed stem design. Each actuation of the cutting oxygen valve mechanism effects a linear axial displacement of the valve stem relative to the torch body and stem packing. Such axial displacement, both on opening and on closing the valve, produces abrasive wear of the stem packing. This eventually results in gas leakage past the packing, from the internal pressurized region to the exterior. Such gaseous oxygen leakage is hazardous due to the resulting oxygen enrichment of the immediate vicinity, which greatly increases the potential for damage or injury should any combustible material be ignited.
A preferred design of a cutting oxygen valve for cutting torches is the diaphragm (packless) type. Such valves incorporate no stem packing and thus are not subject to the inconvenience and hazard of leaking gaseous oxygen. However, a deficiency of the diaphragm type cutting oxygen valves used prior to the present invention has been their inability to produce a controlled gaseous cutting oxygen flow rate proportional to the axial displacement of the valve stem when selectively positioned by the user of the torch. The actual flow rate obtained on actuation of the cutting oxygen valve operating mechanisms of previous cutting torches of the diaphragm type has been virtually the maximum flow rate attainable for the gas pressures and orifice sections employed. Little throttling effect, if any, has been produced.
Thus the prior art has not provided a totally satisfactory design of a cutting torch.